ABSTRACT
Respiratory viral infections are common throughout the year in all age groups and in all countries around the world. Respiratory viruses can cause mild illnesses, such as the common cold, or severe illness such as pneumonia. Both immunocompetent and immunocompromised hosts are affected. Although each respiratory virus can infect both the upper and lower respiratory tract, certain viruses are associated with specific clinical syndromes such as croup or laryngotracheobronchitis.
